Regulation of Hepatic Gluconeogenesis by the Mitochondrial Pyruvate Carrier

 描述(申请人提供)：在进入典型的糖异生途径之前，绝大多数的糖异生碳流通过线粒体基质中的TCA循环进行传递。在正常情况下，线粒体丙酮酸是支持糖异生的关键代谢中间产物。为了到达基质并驱动糖异生，丙酮酸需要一种特定的载体，即线粒体丙酮酸载体(MPC)。因此，MPC占据了连接胞浆、线粒体代谢和糖异生的中心节点。调节肝脏中MPC功能的机制仍不清楚。最近发现的MPC分子使这些机制的研究成为可能。这项建议的总体目标是了解肝脏中MPC功能与T2D期间病理性升高的糖异生之间的关系。这一目标将通过追求两个具体目标来实现：1)确定在禁食和再喂养以及T2D状态下调节肝脏MPC功能的机制；以及2)确定在T2D状态下降低肝脏MPC活性对高血糖的治疗效果。目标1中的研究将检验这一假设，即MPC是转录和翻译后的，在禁食和再喂养过程中都受到激素机制的调节，分别增加和降低MPC的活性，并且MPC在T2D状态的错误调节增加了其活性，从而增加了线粒体丙酮酸的摄取和糖异生。Aim 2中的研究将验证在T2D状态下体内降低肝脏MPC活性的假设 糖异生和改善高血糖。他们还将利用代谢示踪剂确定肝脏特异性MPC基因敲除如何改变正常小鼠、T2D小鼠和原代肝细胞中的糖异生和TCA循环碳流。这项研究意义重大，因为成功完成这项研究将提供有关MPC在推动T2D中升高的肝脏糖异生和由此产生的高血糖中所起作用的基本信息。这项研究具有创新性，因为完成这项研究将产生新的知识，关于MPC分子的调节和功能，作为连接胞质和线粒体代谢与糖异生的关键节点，现在才能获得。我们希望我们的研究将揭示一种新的范式来解释和潜在地减少T2D特征的过度糖异生。

 DESCRIPTION (provided by applicant): Before entering the canonical gluconeogenic pathway, the vast majority of gluconeogenic carbon flux is routed through the TCA cycle within the mitochondrial matrix. Under normal conditions, mitochondrial pyruvate is the key metabolic intermediate supporting gluconeogenesis. To reach the matrix and drive gluconeogenesis, pyruvate requires a specific carrier, the Mitochondrial Pyruvate Carrier (MPC). Thus, the MPC occupies a central node linking cytosolic with mitochondrial metabolism and gluconeogenesis. The mechanisms regulating the function of the MPC in the liver have remained unexplained. The recent identification of the MPC molecule now enables the investigation of these mechanisms. The overall goal of this proposal is to understand the relationship between MPC function in the liver and the pathologically elevated gluconeogenesis during T2D. This goal will be addressed by pursuing two specific aims: 1) Determine the mechanisms that regulate liver MPC function in response to fasting and refeeding and in T2D states; and 2) Determine the therapeutic effect of decreasing Liver MPC activity on hyperglycemia during T2D states. The studies in aim 1 will test the hypothesis that the MPC is transcriptionally and post-translationall regulated by hormonal mechanisms during fasting and refeeding that increase and decrease MPC activity, respectively, and that misregulation of the MPC in T2D states increases its activity thereby increasing mitochondrial pyruvate uptake and gluconeogenesis. The studies in aim 2 will test the hypothesis that decreasing liver MPC activity in vivo during T2D states will decrease gluconeogenesis and ameliorate hyperglycemia. They will also define how liver-specific MPC knockout alters gluconeogenic and TCA cycle carbon flux using metabolic tracers in normal and T2D mice and primary hepatocytes. This research is significant because successful completion will provide fundamental information on the role of the MPC in driving elevated hepatic gluconeogenesis and resultant hyperglycemia in T2D. This research is innovative because completion will generate novel, and now only recently obtainable, knowledge on the regulation and function of the MPC molecule as a critical node linking cytosolic and mitochondrial metabolism with gluconeogenesis. We expect our studies will unveil a new paradigm for explaining and potentially decreasing the excessive gluconeogenesis that characterizes T2D.